Allow setting the definition of 'k' for usage to k=1024 bytes or k=1000 bytes.
Some manufacturers/ISP define 1k=1000bytes.
it is not clear what Tomato uses but I suspect 1k=1024bytes.
Tomato should use GiB if 1k1024 bytes but a better option is to let the user choose GB (1k=1000 bytes) or GiB (1k=1024 byes).